Trump stopped short of calling for a pause in Saudi-led bombing of the country, which is home to what the UN calls the world's worst humanitarian crisis.
But, in a statement, Trump said he had asked aides to contact the Saudi leadership and "to request that they completely allow food, fuel, water, and medicine to reach the Yemeni people who desperately need it."
"This must be done for humanitarian reasons immediately."
Saudi Arabia and its allies have launched a campaign to oust Huthi rebels who control the capital Sanaa and who have links to Riyadh's arch foe Iran.
Seven million people are believed to be on the brink of famine and a cholera outbreak has caused more than 2,000 deaths.
Riyadh has imposed a blockade on Yemen's ports after a Huthi missile was intercepted near Riyadh airport on November 4.
The Trump administration like the Obama administration before it -- has struggled to convince Saudi Arabia, as well as the United Arab Emirates, to pay more heed to the humanitarian crisis.
The conflict has seen civilians repeatedly killed by bombing and through a lack of access to essential food and clean water.
